Slashing Chiller Costs With Inlet Fog

Las Vegas Cogen, Las Vegas, Nevada

The Benefits of MeeFog Technology:

Lower energy bills by limiting the use of the chiller system to only high temperature days

Chiller is enhanced by using fog during the hottest weather

Install MeeFog in this configuration without downtime

Challenge

To limit the usage of the existing chiller in order to control overall cooling costs while achieving maximum turbine output during peaking operation.

Solution

Installed MeeFog™ fogging units upstream of the chiller coil and air filters.

Operate the fog units for power augmentation when temperatures are below 70° F and also use them as pre-cooling for the chiller when temperatures exceed 70° F.

Las Vegas Cogen Las Vegas, Nevada

Las Vegas Cogen is a GE LM 6000-based peaking plant, which starts up hundreds of times per year. The electricity output from this facility is sold to Nevada Power. In addition, thermal energy is used to heat a 12-acre hydroponic greenhouse owned by the company.

The climate in Nevada is warm and dry. The plant is subjected to very hot temperatures during the long summer months. As a result, this facility employs a chiller system to maximize output. However, plant operators found that they couldn’t cool inlet air to dew point during periods of high ambient temperature. A fog system, therefore, was positioned upstream of the chiller coil to act as a pre-cooler.

Installation Challenges/Specifications

As well as being upstream of the chiller coil, the fog system was positioned upstream of the air filters. The main advantage of this positioning was that installation could be accomplished without outage time.

“As it takes time for our chillers to get online, we also use high-pressure inlet fogging of demineralized water to achieve maximum power right away,” said RD Dawkins, Operations.

Supervisor, Las Vegas Cogen. “We use fog exclusively when we first start our combustion turbine and also when it’s below 70 degrees outside. Above that, we also bring on a steam absorption chiller in combination, and the fogging system eliminates the need for a second chiller.”

The fog system consists of 240 nozzles installed in three stages. Operating pressure is 2,000 psi, fog water flow rate is 10.8 gpm and a total of three 5 hp high-pressure pump units were installed.

“Due to its low cost, my advice would be to use fog as much as possible. It is simple, reliable and relatively maintenance free. In fact, the fog system has resulted in less operation of our chillers.” – RD Dawkins, Operations Supervisor, Las Vegas Cogen

Pressure drop associated with the fog nozzle manifold was nominal. The existing heating coil and pad-type prefilters were used as fog droplet filters to remove any unevaporated fog. Although this prevented wetting of the primary air filters, water collected on the cooling coil and prefilter and was drained off, reducing the amount of cooling accomplished by the fog system.

“The MeeFog™ system is low maintenance and very reliable,” said Dawkins. “Even though our fog system is upsteam of the filters, our final barrier filters remain dry and the filters stay cleaner due to the scrubbing effects of the fog.”

Putting it to the Test

Las Vegas Cogen found it far more economical to exclusively use fog under certain conditions. When the outside temperature is below 70° F fog alone is used for cooling. If temperatures rise above 70° F, the steam absorption chiller is used exclusively. But because it takes time for the chillers to come on-line, the cogen facility uses high-pressure inlet fogging to provide maximum power instantly. And again as a precooler to augment the Chiller when ambient temperatures exceed 100° F

Although the fog system was installed upstream of the air filters, the final barrier filters remain dry and these filters stay cleaner due to the scrubbing effects of the mist.

At Las Vegas Cogen, the first cooling stage achieves 7° F of cooling, two stages deliver 12° F and all three provide 15° F. The overall result of fogging is an additional 5 MW of power output.

“Depending on ambient conditions, we achieve around 15 degrees of cooling,” said Stephenson. “Due to its low cost, my advice would be to use fog as much as possible. It is simple, reliable and relatively maintenance free. In fact, the fog system has resulted in less operation of our chillers.”

Fog systems are suitable for use even in very humid climates. It is almost always possible to get at least 15° F of evaporative cooling on a hot day, even in a tropical climate. Mee Industries has developed a climate database tool to help our clients understand how much cooling is available at their particular site. The data is obtained from published climatic databases.

The analysis can be used to determine the Evaporative Cooling Degree Hours (ECDH) for a variety of locations worldwide. The annual ECDH number defines how many degree-hours of cooling can be done at a particular location in a typical year. Hot dry climates can have as much as 50,000 annual ECDH, while even moist climates might have as much as 30,000 ECDH.

About Mee Industries Inc.

Mee Industries Inc. is the innovative, high technology corporation that provides highly customized, cost-effective fog solutions for a wide range of applications including gas turbine inlet air cooling. Founded in 1969 by former Cornell University Research Scientist, Thomas Mee Jr., today the company also specializes in revolutionary fog solutions for industrial humidification, outdoor air conditioning, greenhouse climate control, wine barrel humidification and unique special effects applications.

Renowned MeeFog™ turnkey solutions include meticulously designed and engineered, premium quality, integrated systems that deliver an unequaled combination of price and performance. Mee Industries products are backed by our experienced staff of technical personnel including leading researchers, project managers and engineers along with production and installation specialists. An active research and development division ensures our position of technological leadership in the fog system market. Mee Industries is a proud ISO 9001 certified corporation and manufactures components to meet exacting UL or CE requirements.

Mee Industries is a privately held company with corporate headquarters in Irwindale, Calfornia.